In recent years, more and more attention has been paid to magnetic random access memories (MRAMs) that utilize magnetoresistive effects, as next-generation solid nonvolatile memories which have large capacities and which can perform fast reads and writes and low-power-consumption operations.
MRAM comprises, for example, magnetoresistive elements with ferromagnetic tunnel junctions as storage elements. The magnetoresistive element with a ferromagnetic tunnel junction is also referred to as a MTJ (Magnetic Tunnel Junction) element.
The MTJ element has a three-layer stacked structure comprising a storage layer with a variable magnetization direction, a tunnel barrier layer, and a reference layer that maintains a predetermined magnetization direction. MTJ elements with a four-layer stacked structure including a magnetic field adjustment layer provided on the reference layer are also known.
The magnetic field adjustment layer reduces a magnetostatic leakage field from the reference layer. The magnetic field adjustment layer is, for example, a CoPt (cobalt platinum alloy) layer, the reference layer is, for example, a FeCoB (boron-containing cobalt iron alloy) layer.
When the CoPt layer and the FeCoB layer are processed by well-known process (for example, RIE process or IBE process), conductive etching residue may adhere to sidewalls of the storage layer, the tunnel barrier layer, and the reference layer. The etching residue forms a leakage path between the storage layer and the reference layer. This increases the amount of leakage current between the storage layer and the reference layer.